This project is a continuation of studies on the amino acid sequences of actins from various sources as well as on selected myosins, with the intention of correlating structural features with the functional properties of these proteins. The actins being studied are both cytoplasmic (Acanthamoeba, blood platelet, and brain) and muscle (cardiac and skeletal), and the work is designed to show the precise differences among them. The myosin sequence work is concentrated upon cyanogen bromide peptides from the heavy chains. Two that are being studied first are a 9,000 dalton fragment from the heavy chains. Two that are being studied first are a 9,000 dalton fragment from the myosin "head" that contains the single residue of N tau-methylhistidine and probably participates in one of the active sites of myosin, and a 22,000 dalton peptide that arises from the COOH-terminal region of myosin. This peptide is a "coiled-coil," and probably contains the information for self-assembly of the myosin molecules into the thick filament. BIBLIOGRAPHIC REFERENCES: Elzinga, M., Maron, B.J. and Adelstein R.S. (1976), Human Heart and Platelet Actins Are Products of Different Genes, Science 191, 94-95. Lu, R., and Elzinga, M. (1976), Comparison of Amino Acid Sequences of Brain and Muscle Actins, Fed. Proc. 35, 1359.